1. Field of the Invention
The present invention relates to a method of improving the compatibility of a fuel additive composition. In particular, the present invention improves the compatibility of the fuel additive composition by blending together a fuel additive composition containing a Mannich condensation product, a hydrocarbyl-terminated poly(oxyalkylene) monool and a certain combination of a carboxylic acid and an anhydride.
2. Description of the Related Art
Mannich condensation products are known in the art as fuel additives for the prevention and control of engine deposits. For example, U.S. Pat. No. 4,231,759, issued Nov. 4, 1980 to Udelhofen et al., discloses reaction products obtained by the Mannich condensation of a high molecular weight alkyl-substituted hydroxyaromatic compound, an amine containing an amino group having at least one active hydrogen atom, and an aldehyde, such as formaldehyde. This patent further teaches that such Mannich condensation products are useful detergent additives in fuels for the control of deposits on carburetor surfaces and intake valves.
Generally, Mannich condensation products are utilized in combination with other fuel additive components. For example, polyolefins and polyether compounds are also well known in the art as fuel additives. It is not uncommon for the literature to refer to the enhanced benefits of the combination of two or more such fuel additives for the prevention and control of engine deposits.
U.S. Pat. No. 5,405,419, issued Apr. 11, 1995 to Ansari et al., discloses a fuel additive composition comprising (a) a fuel-soluble aliphatic hydrocarbyl-substituted amine having at least one basic nitrogen atom wherein the hydrocarbyl group has a number average molecular weight of about 700 to 3,000; (b) a polyolefin polymer of a C2 to C6 monolefin, wherein the polymer has a number average molecular weight of about 350 to 3,000; and (c) a hydrocarbyl-terminated poly(oxyalkylene) monool having an average molecular weight of about 500 to 5,000. This patent further teaches that fuel compositions containing these additives will generally contain about 50 to 500 ppm by weight of the aliphatic amine, about 50 to 1,000 ppm by weight of the polyolefin and about 50 to 1,000 ppm by weight of the poly(oxyalkylene) monool. This patent also discloses that fuel compositions containing 125 ppm each of aliphatic amine, polyolefin and poly(oxyalkylene) monool provide better deposit control performance than compositions containing 125 ppm of aliphatic amine plus 125 ppm of poly(oxyalkylene) monool.
In fuel additive applications, the presence of small amounts of low molecular weight amine in dispersant components such as the Mannich condensation product can lead to formulation incompatibilities (for example, with certain corrosion inhibitors or demulsifiers) and air sensitivity (for example, reaction with carbon dioxide in the air). For example, corrosion inhibitors are typically complex mixtures of organic acids of wide molecular weight range. These can react with trace amounts of low molecular weight amines in the Mannich component at room temperature to form insoluble salts and at higher temperatures to form insoluble amides. Formulation incompatibility and air sensitivity are manifested by formation of haze, floc, solids, and/or gelatinous material in the formulation over time. The incompatibility may occur in the absence of air. Consequently, the manufacturing process for amine dispersant type fuel additives may include a step to remove low molecular weight amines to low levels, or the compatibility issue may be addressed during formulation. However, the unique chemistry of Mannich condensation products must be considered with either approach. In particular, the chemical equilibrium can generate additional low molecular weight amines if the product is heated too much during the purification step or after a formulation has been prepared. Therefore, there is a need for either an economical process to reduce the unconsumed amine and the amine-formaldehyde intermediate to a low level after the Mannich reaction or a chemical scavenger that renders the water-soluble amine harmless to formulation compatibility and that reduces formulation air sensitivity.
U.S. Pat. No. 3,798,247 issued Mar. 19, 1974 to Piasek and Karil, discloses that the reaction under Mannich condensation conditions, like other chemical reactions, does not go to theoretical completion and some portion of the reactants, generally the amine, remains unreacted or only partially reacted as a coproduct. Unpurified products of Mannich processes also commonly contain small amounts of insoluble particle byproducts of the Mannich condensation reaction that appear to be the high molecular weight condensation product of formaldehyde and polyamines. The amine and amine byproducts lead to haze formation during storage and, in diesel oil formulations, to rapid buildup of diesel engine piston ring groove carbonaceous deposits and skirt varnish. The insoluble or borderline soluble byproducts are substantially incapable of removal by filtration and severely restrict product filtration rate. These drawbacks were overcome by adding long-chain carboxylic acids during the reaction to reduce the amount of solids formation from the Mannich reaction. This was thought to render the particulate polyamine-formaldehyde condensation product soluble through formation of amide-type links. In particular, oleic acid worked well at 0.1 to 0.3 mole/mole of alkylphenol. The quantity of unconsumed or partially reacted amine was not mentioned in the patent.
U.S. Pat. No. 4,334,085, issued Jun. 6, 1982 to Basalay and Udelhofen, discloses that Mannich condensation products can undergo transamination, and use this to solve the problem of byproduct amine-formaldehyde resin formation encountered in U.S. Pat. No. 3,798,247 eliminating the need for using a fatty acid. U.S. Pat. No. 4,334,085 defined transamination as the reaction of a Mannich adduct based on a single-nitrogen amine with a polyamine to exchange the polyamine for the single-nitrogen amine. The examples in this patent infer that the unconsumed amine and partially reacted amine discussed in U.S. Pat. No. 3,798,247 are not merely unconsumed, but must be in chemical equilibrium with the product of the Mannich condensation reaction. In Example 1 of U.S. Pat. No. 4,334,085, a Mannich condensation product is made from 0.5 moles of polyisobutylphenol, 1.0 mole of diethylamine and 1.1 moles of formaldehyde. To 0.05 moles of this product was added 0.05 moles of tetraethylenepentamine (TEPA) and then the mixture was heated to 155xc2x0 C. while blowing with nitrogen. The TEPA replaced 80 to 95% of the diethylamine in the Mannich as the nitrogen stripped off the diethylamine made available by the equilibrium with the Mannich.
U.S. Pat. No. 5,360,460, issued Nov. 1, 1994 to Mozdzen et al., discloses a fuel additive composition comprising (A) an alkylene oxide condensate or the reaction product thereof and an alcohol, (B) a monocarboxylic fatty acid, and (C) a hydrocarbyl amine, or the reaction product thereof and an alkylene oxide. The fuel additive composition deals with cleaning of injection ports, lubricating a fuel line system in a diesel vehicle, and with minimizing corrosion in the fuel line system. However, the use of a Mannich condensation product is neither disclosed nor suggested.
We have discovered a novel method of improving the compatibility of a fuel additive composition by blending together a fuel additive composition containing a Mannich condensation product, a hydrocarbyl-terminated poly(oxyalkylene) monool, and a certain combination of a carboxylic acid and an anhydride.
Accordingly, the present invention provides a novel method of improving the compatibility of a fuel additive composition comprising blending together the following components:
a) a Mannich condensation product of (1) a high molecular weight alkyl-substituted hydroxyaromatic compound wherein the alkyl group has a number average molecular weight of from about 300 to about 5,000 (2) an amine having the formula: 
xe2x80x83wherein A is CH or nitrogen, R1, R2, R3 are independently hydrogen or lower alkyl of 1 to about 6 carbon atoms and each R2 and R3 is independently selected in each xe2x80x94CR2R3xe2x80x94 unit, and x is an integer from 1 to about 6;
xe2x80x83and (3) an aldehyde, wherein the respective molar ratio of reactants (1), (2), and (3) is 1:0.1-2.0:0.1-2.0;
b) a hydrocarbyl-terminated poly(oxyalkylene) monool having an average molecular weight of about 500 to about 5,000, wherein the oxyalkylene group is a C2 to C5 oxyalkylene group and the hydrocarbyl group is a C1 to C30 hydrocarbyl group;
c) a carboxylic acid as represented by the formula:
R4(COOH)y 
xe2x80x83wherein R4 represents a hydrocarbyl group having about 2 to about 50 carbon atoms, and y represents an integer of 1 to about 4; and
d) an anhydride selected from the group consisting of succinic, glutaric, phthalic, and alkyl anhydrides.
Among other factors, the present invention is based on the surprising discovery that the formulation compatibility is greatly improved by the combination of a selected carboxylic acid and anhydride that interacts with the residual amine. Typically, the residual amines are small quantities of low molecular weight amine and amine-formaldehyde intermediates in the Mannich which interact with organic acid mixtures that are typically used in fuel additive formulations to provide anti-corrosion properties. The low molecular weight amines can also interact with carbon dioxide from exposure of the formulation to air. The interaction can lead to formation of insoluble material, haze, and flocs. In addition, the selected carboxylic acid and anhydride provides anti-corrosion properties. Thus, the improved compatibility and air sensitivity manifests itself in less insoluble material, haze, and flocs.
The novel method of the present invention improves the compatibility of a fuel additive composition by blending together a fuel additive composition containing a Mannich condensation product, a hydrocarbyl-terminated poly(oxyalkylene) monool, and a certain combination of a carboxylic acid and an anhydride.
Prior to discussing the present invention in detail, the following terms will have the following meanings unless expressly stated to the contrary.
The term xe2x80x9chydrocarbylxe2x80x9d refers to an organic radical primarily composed of carbon and hydrogen which may be aliphatic, alicyclic, aromatic or combinations thereof, e.g., aralkyl or alkaryl. Such hydrocarbyl groups may also contain aliphatic unsaturation, i.e., olefinic or acetylenic unsaturation, and may contain minor amounts of heteroatoms, such as oxygen or nitrogen, or halogens, such as chlorine. When used in conjunction with carboxylic fatty acids, hydrocarbyl will also include olefinic unsaturation.
The term xe2x80x9calkylxe2x80x9d refers to both straight- and branched-chain alkyl groups.
The term xe2x80x9calkylenexe2x80x9d refers to straight- and branched-chain alkylene groups having at least 1 carbon atom. Typical alkylene groups include, for example, methylene (xe2x80x94CH2xe2x80x94), ethylene (xe2x80x94CH2CH2xe2x80x94), propylene (xe2x80x94CH2CH2CH2xe2x80x94), isopropylene (xe2x80x94CH(CH3)CH2xe2x80x94), n-butylene (xe2x80x94CH2CH2CH2CH2xe2x80x94), sec-butylene (xe2x80x94CH(CH2CH3)CH2xe2x80x94), n-pentylene (xe2x80x94CH2CH2CH2CH2CH2xe2x80x94), and the like.
The term xe2x80x9cpolyoxyalkylenexe2x80x9d refers to a polymer or oligomer having the general formula: 
wherein Ra and Rb are each independently hydrogen or lower alkyl groups, and c is an integer from about 5 to about 100. When referring herein to the number of oxyalkylene units in a particular polyoxyalkylene compound, it is to be understood that this number refers to the average number of oxyalkylene units in such compounds unless expressly stated to the contrary.
The term xe2x80x9cfuelxe2x80x9d or xe2x80x9chydrocarbon fuelxe2x80x9d refers to normally liquid hydrocarbons having boiling points in the range of gasoline and diesel fuels.
Mannich reaction products employed in this invention are obtained by condensing an alkyl-substituted hydroxyaromatic compound whose alkyl-substituent has a number average molecular weight of from about 300 to about 5,000, preferably polyalkylphenol whose polyalkyl substituent is derived from 1-mono-olefin polymers having a number average molecular weight of from about 300 to about 5,000, more preferably from about 400 to about 3,000; a cyclic amine containing a primary and secondary amino group or two secondary amino groups; and an aldehyde, preferably formaldehyde, in the presence of a solvent.
The overall reaction may be illustrated by the following: 
wherein A, R1, R2, R3 and x are as defined herein.
High molecular weight Mannich reaction products useful as additives in the fuel additive compositions of this invention are preferably prepared according to conventional methods employed for the preparation of Mannich condensation products, using the above-named reactants in the respective molar ratios of high molecular weight alkyl-substituted hydroxyaromatic compound, amine, and aldehyde of approximately 1:0.1-2.0:0.1-2.0. Preferably, the respective molar ratios will be 1:0.5-1.5:0.5-1.5. More preferably, the respective molar ratios will be 1:0.8-1.3:0.8-1.3. A suitable condensation procedure involves adding at a temperature of from room temperature to about 95xc2x0 C., the formaldehyde reagent (e.g., formalin) to a mixture of amine and alkyl-substituted hydroxyaromatic compounds alone or in an easily removed organic solvent, such as benzene, xylene, or toluene or in solvent-refined neutral oil, and then heating the reaction mixture at an elevated temperature (about 120xc2x0 C. to about 175xc2x0 C.) while the water of reaction is distilled overhead and separated. The reaction product so obtained is finished by filtration and dilution with solvent as desired.
The most preferred Mannich reaction product additives employed in this invention are derived from high molecular weight Mannich condensation products, formed by reacting an alkylphenol, an amine of the present invention, and a formaldehyde affording reactants in the respective molar ratio of 1:1:1.05, wherein the alkyl group of the alkylphenol has a number average weight of from about 300 to about 5,000.
Representative of the high molecular weight alkyl-substituted hydroxyaromatic compounds are polypropylphenol, polybutylphenol, and other polyalkylphenols, with polyisobutylphenol being the most preferred. Polyalkylphenols may be obtained by the alkylation, in the presence of an alkylating catalyst such as BF3, of phenol with high molecular weight polypropylene, polybutylene, and other polyalkylene compounds to give alkyl substituents on the benzene ring of phenol having a number average molecular weight of from about 300 to about 5,000.
The alkyl substituents on the hydroxyaromatic compounds may be derived from high molecular weight polypropylenes, polybutenes, and other polymers of mono-olefins, principally 1-mono-olefins. Also useful are copolymers of mono-olefins with monomers copolymerizable therewith, wherein the copolymer molecule contains at least about 90% by weight of mono-olefin units. Specific examples are copolymers of butenes (1-butene, 2-butene, and isobutylene) with monomers copolymerizable therewith wherein the copolymer molecule contains at least about 90% by weight of propylene and butene units, respectively. Said monomers copolymerizable with propylene or said butenes include monomers containing a small proportion of unreactive polar groups, such as chloro, bromo, keto, ether, or aldehyde, which do not appreciably lower the oil-solubility of the polymer. The comonomers polymerized with propylene or said butenes may be aliphatic and can also contain non-aliphatic groups, e.g., styrene, methylstyrene, p-dimethylstyrene, divinyl benzene, and the like. From the foregoing limitation placed on the monomer copolymerized with propylene or said butenes, it is clear that said polymers and copolymers of propylene and said butenes are substantially aliphatic hydrocarbon polymers. Thus, the resulting alkylated phenols contain substantially alkyl hydrocarbon substitutents having a number average molecular weight of from about 300 to about 5,000.
In addition to the foregoing high molecular weight hydroxyaromatic compounds, other phenolic compounds which may be used include, high molecular weight alkyl-substituted derivatives of resorcinol, hydroquinone, cresol, cathechol, xylenol, hydroxy-di-phenyl, benzylphenol, phenethylphenol, naphthol, tolylnaphthol, among others. Preferred for the preparation of such preferred Mannich condensation products are the polyalkylphenol reactants, e.g., polypropylphenol and polybutylphenol, particularly polyisobutylphenol, whose alkyl group has a number average molecular weight of about 300 to about 5,000, preferably about 400 to about 3,000, more preferably about 500 to about 2,000, and most preferably about 700 to about 1,500.
As noted above, the polyalkyl substituent on the polyalkyl hydroxyaromatic compounds employed in the invention may be generally derived from polyolefins which are polymers or copolymers of mono-olefins, particularly 1-mono-olefins, such as ethylene, propylene, butylene, and the like. Preferably, the mono-olefin employed will have about 2 to about 24 carbon atoms, and more preferably, about 3 to about 12 carbon atoms. More preferred mono-olefins include propylene, butylene, particularly isobutylene, 1-octene and 1-decene. Polyolefins prepared from such mono-olefins include polypropylene, polybutene, especially polyisobutene, and the polyalphaolefins produced from 1-octene and 1-decene.
The preferred polyisobutenes used to prepare the presently employed polyalkyl hydroxyaromatic compounds are polyisobutenes which comprise at least about 20% of the more reactive methylvinylidene isomer, preferably at least about 50% and more preferably at least about 70% methylvinylidene isomer. Suitable polyisobutenes include those prepared using BF3 catalysts. The preparation of such polyisobutenes in which the methylvinylidene isomer comprises a high percentage of the total composition is described in U.S. Pat. Nos. 4,152,499 and 4,605,808.
Examples of suitable polyisobutenes having a high alkylvinylidene content include Ultravis 10, a polyisobutene having a molecular weight of about 950 and a methylvinylidene content of about 76%, and Ultravis 30, a polyisobutene having a molecular weight of about 1,300 and a methylvinylidene content of about 74%, both available from British Petroleum, and Glissopal 1000, 1300, and 2200, available from BASF.
The preferred configuration of the alkyl-substituted hydroxyaromatic compound is that of a para-substituted mono-alkylphenol. However, any alkylphenol readily reactive in the Mannich condensation reaction may be employed. Accordingly, ortho mono-alkylphenols and dialkylphenols are suitable for use in this invention.
The amine of the present invention contains both a primary and secondary amino group or two secondary amino groups. The general structure of the amine is illustrated by the following formula: 
wherein A is CH or nitrogen, R1, R2, R3 are independently hydrogen or lower alkyl having from 1 to about 6 carbon atoms, and x is an integer 1 to about 6. Preferably, A is CH or nitrogen, R1 is hydrogen, R2 and R3 are independently hydrogen or lower alkyl having from 1 to about 4 carbon atoms, and x is an integer 1 to about 4. More preferably, A is CH or nitrogen, R1, is hydrogen, R2 and R3 are independently hydrogen or lower alkyl having from 1 to about 2 carbon atoms, and x is an integer of about 2. Most preferably, A is nitrogen, R1, R2, R3 are hydrogen, and x is an integer of about 2. In each of the preceding, each R2 and R3 is independently selected in each xe2x80x94CR2R3xe2x80x94 unit.
Examples of amines are 1-piperazinemethanamine, 1-piperazineethanamine, 1-piperazinepropanamine, 1-piperazinebutanamine, xcex1-methyl-1-piperazinepropanamine, N-ethyl-1-piperazineethanamine, N-(1,4-dimethylpentyl)-1-piperazineethanamine, 1-[2-(dodecylamino)ethyl]-piperazine, 1-[2-(tetradecylamino)ethyl]-piperazine, 4-piperidinemethanamine, 4-piperidineethanamine, 4-piperidinebutanamine, and N-phenyl-4-piperidinepropanamine. The most preferred amine of the Mannich condensation product of the present invention is 1-piperazineethanamine or 1-(2-aminoethyl)piperazine (AEP).
Representative aldehydes for use in the preparation of the high molecular weight Mannich reaction products employed in this invention include the aliphatic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, valeraldehyde, caproaldehyde, heptaldehyde, and stearaldehyde. Aromatic aldehydes which may be used include benzaldehyde and salicylaldehyde. Illustrative heterocyclic aldehydes for use herein are furfural and thiophene aldehyde, etc. Also useful are formaldehyde-producing reagents such as paraformaldehyde, or aqueous formaldehyde solutions such as formalin. Most preferred is formaldehyde or formalin.
The hydrocarbyl-terminated poly(oxyalkylene) polymers employed in the present invention are monohydroxy compounds, i.e., alcohols, often termed monohydroxy polyethers, or polyalkylene glycol monohydrocarbylethers, or xe2x80x9ccappedxe2x80x9d poly(oxyalkylene) glycols and are to be distinguished from the poly(oxyalkylene) glycols (diols), or polyols, which are not hydrocarbyl-terminated, i.e., not capped. The hydrocarbyl-terminated poly(oxyalkylene) alcohols are produced by the addition of lower alkylene oxides, such as ethylene oxide, propylene oxide, the butylene oxides, or the pentylene oxides to the hydroxy compound R2OH under polymerization conditions, wherein R2 is the hydrocarbyl group which caps the poly(oxyalkylene) chain. Methods of production and properties of these polymers are disclosed in U.S. Pat. Nos. 2,841,479 and 2,782,240 and Kirk-Othmer""s xe2x80x9cEncyclopedia of Chemical Technologyxe2x80x9d, 2nd Ed Volume 19, p. 507. In the polymerization reaction, a single type of alkylene oxide may be employed, e.g., propylene oxide, in which case the product is a homopolymer, e.g., a poly(oxyalkylene) propanol. However, copolymers are equally satisfactory and random copolymers are readily prepared by contacting the hydroxyl-containing compound with a mixture of alkylene oxides, such as a mixture of propylene and butylene oxides. Block copolymers of oxyalkylene units also provide satisfactory poly(oxyalkylene) polymers for the practice of the present invention. Random polymers are more easily prepared when the reactivities of the oxides are relatively equal. In certain cases, when ethylene oxide is copolymerized with other oxides, the higher reaction rate of ethylene oxide makes the preparation of random copolymers difficult. In either case, block copolymers can be prepared. Block copolymers are prepared by contacting the hydroxyl-containing compound with first one alkylene oxide, then the others in any order, or repetitively, under polymerization conditions. A particular block copolymer is represented by a polymer prepared by polymerizing propylene oxide on a suitable monohydroxy compound to form a poly(oxypropylene) alcohol and then polymerizing butylene oxide on the poly(oxyalkylene) alcohol.
In general, the poly(oxyalkylene) polymers are mixtures of compounds that differ in polymer chain length. However, their properties closely approximate those of the polymer represented by the average composition and molecular weight.
The polyethers employed in this invention can be represented by the formula:
R5Oxe2x80x94(R6O)zxe2x80x94H 
wherein R5 is a hydrocarbyl group of from 1 to about 30 carbon atoms; R6 is a C2 to C5 alkylene group; and z is an integer such that the molecular weight of the polyether is from about 500 to about 5,000.
Preferably, R5 is a C7 to C30 alkylphenyl group. Most preferably, R5 is dodecylphenyl.
Preferably, R6 is a C3 or C4 alkylene group. Most preferably, R6 is a C3 alkylene group.
Preferably, the polyether has a molecular weight of from about 750 to about 3,000; and more preferably from about 900 to about 1,500.
The method of the present invention further involves a carboxylic acid compound. The carboxylic acid to be employed in the invention preferably may be represented by the formula:
R4(COOH)y 
wherein R4 represents a hydrocarbyl group having about 2 to about 50 carbon atoms, and y represents an integer of 1 to about 4.
The preferred hydrocarbyl groups are aliphatic groups, such as an alkyl group or an alkenyl group, which may have a straight chain or a branched chain. Examples of preferred carboxylic acids are aliphatic acids having about 8 to about 30 carbon atoms and include caprylic acid, pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, isostearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, montanic acid, melissic acid, caproleic acid, palmitoleic acid, oleic acid, eraidic acid, linolic acid, linoleic acid, fatty acid or coconut oil, fatty acid of hardened fish oil, fatty acid of hardened rapeseed oil, fatty acid of hardened tallow oil, and fatty acid of hardened palm oil. Preferably, the carboxylic acid is oleic acid.
The method of the present invention also involves an anhydride. The anhydride employed in the present invention is preferably an anhydride selected from the group consisting of succinic, glutaric, phthalic, and alkyl an hydrides. Examples of such anhydrides are illustrated by the following structures: 
wherein R7-R15 are independently hydrogen or hydrocarbyl having about 2 to about 50 carbon atoms, provided that R14 and R15 are both alkyl. The preferred hydrocarbyl groups are aliphatic groups, such as an alkyl group or an alkenyl group, which may have a straight chain or a branched chain. Examples of preferred anhydrides are substituted succinic, glutaric, phthalic, and simple alkyl anhydrides having about 8 to about 30 carbon atoms in the substituent groups and include tetrapropenylsuccinic anhydride, polyisobutenylsuccinic anhydride, polyisopropenylsuccinic anhydride, dodecenylglutaric anhydride, tetrapropenylglutaric anhydride dodecenylphthalic anhydride, tetrapropenylphthalic anhydride, octanoic anydride, nonanoic anhydride, and decanoic anhydride. Preferably, the anhydride is tetrapropenylsuccinic anhydride.
The method of the present invention provides improved compatibility of a fuel additive composition which comprises blending together the following components:
a) a Mannich condensation product of (1) a high molecular weight alkyl-substituted hydroxyaromatic compound wherein the alkyl group has a number average molecular weight of from about 300 to about 5,000 (2) an amine having the formula: 
xe2x80x83wherein A, R1, R2, R3 and x are as defined herein;
xe2x80x83and (3) an aldehyde, wherein the respective molar ratio of reactants (1), (2), and (3) is 1:0.1-2.0:0.1-2.0;
b) a hydrocarbyl-terminated poly(oxyalkylene) monool having an average molecular weight of about 500 to about 5,000, wherein the oxyalkylene group is a C2 to C5 oxyalkylene group and the hydrocarbyl group is a C, to C30 hydrocarbyl group;
c) a carboxylic acid as represented by the formula:
R4(COOH)y 
xe2x80x83wherein R4 represents a hydrocarbyl group having about 2 to about 50 carbon atoms, and y represents an integer of 1 to about 4; and
d) an anhydride selected from the group consisting of succinic, glutaric, phthalic, and alkyl anhydrides.
Preferably, the Mannich condensation product, hydrocarbyl-terminated poly(oxyalkylene) monool, carboxylic acid, and anhydride are blended together at a temperature in the range of about room temperature (about 20xc2x0 C.) to about 100xc2x0 C.
In general, the total amount of carboxylic acid is 1 to about 15%, more preferably about 2 to about 10%, most preferably about 3 to about 8% of the weight of the Mannich condensation product, or there is typically about 0.2 to about 2.5, more preferably, about 0.3 to about 1.6, most preferably, about 0.5 to about 1.3, equivalents of carboxylic acid per equivalent of water-soluble amine in the Mannich condensation product.
In general, the total amount of an hydride is about 0.6 to about 6.0%, more preferably about 0.9 to about 4.5%, most preferably about 1.8 to about 3.0% of the weight of the Mannich condensation product, or there is typically about 0.2 to about 2.0, more preferably, about 0.3 to about 1.5, most preferably, about 0.6 to about 1.0, equivalent of an hydride per equivalent of water-soluble amine in the Mannich condensation product.
The carboxylic acid and anhydride treatment of the Mannich condensation product of the present invention provides improved compatibility with other additives in the desired finished fuel additive composition. Compatibility in this instance generally means that the components in the present invention as well as being fuel soluble in the applicable treat rate also do not cause other additives to precipitate under normal conditions. The improved compatibility manifests itself in less insoluble material such as haze and sediment.